Fix schema update with notedb-read enabled

Unwrap the db (as done for RebuildNoteDb as well), to ensure
we can access the underlying db.

Bug: Issue 4164
Change-Id: Id9cf05fddf9f5d7d09e5664276a15fddc0690d36

gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaUpdater.java

@@ -92,7 +92,8 @@ public class SchemaUpdater {
   }
 
   public void update(final UpdateUI ui) throws OrmException {
-    try (ReviewDb db = schema.open()) {
+    try (ReviewDb db = unwrap(schema.open())) {
+
       final SchemaVersion u = updater.get();
       final CurrentSchemaVersion version = getSchemaVersion(db);
       if (version == null) {
@@ -114,6 +115,13 @@ public class SchemaUpdater {
     }
   }
 
+  private static ReviewDb unwrap(ReviewDb db) {
+    if (db instanceof DisabledChangesReviewDbWrapper) {
+      db = ((DisabledChangesReviewDbWrapper) db).unsafeGetDelegate();
+    }
+    return db;
+  }
+
   private CurrentSchemaVersion getSchemaVersion(final ReviewDb db) {
     try {
       return db.schemaVersion().get(new CurrentSchemaVersion.Key());